Dynamic Fuel Flowmeters Calibration Using A Double Nozzle Flapper Valve For Excitation Flow

Fuel flow rate is one of the main control variables in aeroengine control loops.Both reliable engine operation and ground testing are based on accurate measurements to the flow rate.Wear and corrosion on flowmeters after a period of their service can easily lead to changes in the meter factors,which necessitates the periodical calibration on the flowmeters.For a long time,due to the lack of a dynamic calibration system,most of the flowmeters on duty are up against steady-state calibration but dynamic usage in flow rate measurement,which seriously affects the confidence of dynamic measurement of fuel flow rates.Therefore,it's significance in theory and practice for improving the overall level of ground tests to conduct researches on the testing techniques of dynamic flowmeter performance.This thesis presents a method using piezoelectric stack driven double nozzle-flapper valve to produce excitation flow in pipeline,and its initial application in dynamic calibration of flowmeters.It works by comparing the rapidly changing excitation flow with the reading of the calibrated flowmeter and calculating the dynamic meter coefficient.This thesis proposes the principle and the system composition first.CFD numerical simulation for the calibration fuel flow circuit is carried out and the flow excitation process is analyzed from the perspective of pressure transmission.A simplified flowmeter model is constructed by using Matlab/Simulink.Combining the model with the inlet flow rate through CFD simulation yields the theoretical value of the flowmeter reading.Taking the system lag into account,the response and the time constant of the calibrated flowmeter are calculated.Based on the mathematical equation and numerical simulation,the dynamic meter factor of about 0.2534 mL for the calibrated turbine flowmeter is obtained.Finally,an experimental device of flow excitation for dynamic calibration is designed and verified on a dedicated test bench of aero fuel servovalves.The flapper displacement is adjusted by varying the drive voltage applied to the piezoelectric stack to generate different excitation flows,and the excitation characteristics and calibration results are analyzed based on the measured flapper displacement,the control chamber pressure and the flow meter output values.It is shown that the experimental response time and excitation process are basically consistent with the simulated results,and that the flow excitation system proposed in this paper is feasible,which provides a reference to develop the dynamic calibration system for flowmeters ranged from the small to the medium flow rate.